ANSWER
900 feet
Step-by-step explanation
We have that the bird is initially flying 1200ft above sea level. Then, it drops 500ft closer to the sea level and finally, rises 200ft back up,
When it drops 500ft, the new altitude of the bird is,

And then, since it rises 200ft back up, the final altitude of the bird is,

Hence, the bird is now flying 900 feet above sea level.